Disk applied duo-servo



May 7, 1963 R. 'r. BURNETT DISH APPLIED DUO-SERVO 2 Sheets-Sheet 1 Original Filed June 1, 1954 ll /4 70 INVENTOR.

ATTO/PA/f y 7, 1963 R. T. BURNETT 3,088,551

DISH APPLIED DUO-SERVO Original Filed June 1. 1954 2 Sheets-Sheet 2 64 40/ 3a 55 g H 66 28 33 g? O 56 22 5? .36 /4 26 FEB IN V EN TOR.

BYWNHM nrrae er aired States 3,088,551 Patented May 7, 1963 free 1 3,088,551 DISK APPLIED DUO-SERVO Richard T. Burnett, South Bend, Ind, assignor to The Bendix Corporation, a corporation of Deiaware Original application June 1, 1954, Ser. No. 433,609, new Patent No. 2,927,664, dated Mar. 8, 1960. Divide-1i and this application Feb. 29, 1960, Ser. No. 11,596

3 Claims. (Cl. 188-70) This invention relates to improvements in brakes of the type combining disk and drum brake features.

This application is a division of my copending application No. 433,609, filed June 1, 1954, now Patent No. 2,927,664, granted March 8, 1960.

In the construction of the brake of the invention many of the advantages of both drum and disk brakes have been incorporated and most of the disadvantages either eliminated or reduced in effectiveness by rearrangement of the parts.

An object of the invention is to provide a combined disk and shoe brake unit in which the disk element is fioatably mounted on the shoe element and operatively connected thereto so that axial movement of the disk element into frictional engagement with a rotatable member imparts a substantially radial movement to the shoe element to thereby establish frictional engagement between said shoe element and said rotatable member.

Another object of the invention is to provide a brake having a combined disk and shoe brake unit operatively connected to a fluid motor via a lever system pivotally interposed between said motor and said disk.

A still further object of the invention is to provide a brake employing two interdependent self energizing friction elements engageable with arcuate and plane surfaces of a rotatable member.

A very important object is to combine in a disk and shoe brake the following salient features: (1) a self-energizing disk element, (2) a shoe element actuable by the disk element, and (3) a hydraulic fluid motor situated so as to be effected the least by heat developed in the brake.

The above and other objects and features of the invention will be apparent from the following description of the device taken in connection with the accompanying drawings which form a part of the specification and in which:

FIGURE 1 is a side elevation of the brake of my invention with one side of the drum and the disk element on the right side removed to show the brake actuating mechanism more clearly;

FIGURE 2 is a view taken on the line 2-2 of FIG- URE 1;

FIGURE 3 is a view taken on the line 4-4 of FIG URE 1; and

FIGURE 4 is a View partly in section taken on the line 44 of FIGURE 1; and

FIGURE 5 is a view partly in section taken on the line 5-5 of FIGURE 1.

Referring to FIGURES 1 and 2 of the drawings the reference numeral designates a wheel brake assembly comprising a rotatable member 12 which is secured to a wheel, not shown, and a fixed member 14 adapted to be fastened to a vehicle structure, not shown. The braking surface portion of the rotatable member can be described as U-shaped in cross section since it comprises a cylindrical portion 16 and parallel side portions 18 and 20. The side portions 18 and 20 provide plane or flat surfaces lying in parallel planes angularly displaced at substantially right angles to the cylindrical surface formed in said cylindrical portion 16. To simplify assembly of the brake the rotatable member 12 is constructed so that the side 20 is removably mounted thereon by bolts 22 which pass through flanges 24 and 26 of the side 20 and cylindrical portion 16, respectively. The rotatable member and details of construction are claimed and described in my application Serial No. 434,846, filed June 7, 1954, now abandoned.

In order to check or retard the motion of the rotatable member 12, a friction device or unit 28 is pivotally supported on an anchor member 30 located radially inwardly from the aforesaid plane and cylindrical surfaces of said rotatable member and suitably attached to the fixed member 14. There are two such units 255 suitably positioned around the fixed member for frictionally engaging the rotatable member. The two friction units are arranged so as to be energized when rotation of the member 12 is in the direction of the arrow, that is, counterclockwise as viewed in FIGURE 1. Since the units 28 are of identical construction only one will be described in detail.

It will be observed (FIGURE 2) that the fixed member 14 is formed so that the portion 32 to which the anchor 30 is secured is offset from the back portion 34 thus placing the offset portion 32 near the plane through which the braking forces act on the anchor 30. This construction of the fixed member results in a compact and durable mounting for the friction unit and keeps to a minimum offset loading on the anchor member.

The friction unit or device includes a friction or shoe element 36 having a web portion 38 and an arcuate plate or rim portion 4i) suitably attached to the web. The web is provided with an opening 42 through which the anchor member 30 extends. The friction element 36 is retained in place against the offset portion 32 by a dished washer 44 and a C-ring 46 removably fit into groove 48 of the anchor member. A torsion spring 50 is carried at the outer end of the anchor member, with one end 49 of the spring urged against the offset portion 32 of the fixed member and the other end or free end 51 of the spring engaging the web 38 of the friction element for rotating the same in a clockwise direction as viewed in FIGURE 1. The friction unit includes two other friction or disk elements 52 operatively connected to the first mentioned friction element through a ball and ramp arrangement comprising an inner section 54 mounted in a bushing 56 carried by the friction element 36 and outer sections 58 pressed into side plates 68. The inner and outer sections are formed with cam surfaces or ramps between which balls 60 are interposed. The second mentioned friction elements 52 are held in assembled relationship to the first friction element by a U-shaped spring clamp 59 (see FIG. 4) the ends of which are bifurcated in order to straddle the reduced diameter end portions 61 of the outer sections 58. The closed end 62 of the clamp rides in a slot 63 of the web 38. Any relative movement of the first and second friction elements from the position of FIGURE 2 will cause the balls 60 to ride upon the ramps thus imparting axial or lateral movement to the second friction elements. The first friction element 36 is equipped with brake lining material 64 appropriately fastened to the plate 40 and the second friction elements 52 are furnished with brake lining material 66 secured to the fiat side plates 68 extending circumferentially along the sides 18 and 20 of the rotatable member.

For actuating the friction unit 28 a fluid motor 70, as best seen in FIG. 3 is mounted on the fixed member 14 at a point radially inward from the friction engaging surfaces and sufliciently remote from the elements of the brake which generate considerable heat during a brake application to minimize heat transfer to said fluid motor. The fluid motor 70 includes a housing 72 formed with an axial extending slot 74 in the side wall. The friction unit 28 is connected to the fluid motor 70 via lever means including two levers 76 passing through the slot 74. In the drawing the levers are illustrated as force multiplying but this is a design expedient and they can, for example, have a one to one ratio. The ends of the levers extending into the housing are rockably connected to a stationary the end member 78, piston 80, and plates 68 respectively.

A link 85 interposed between the levers provides a fulcrum about which the levers are rotated when the piston 80 is moved. An O-ring 87 located in the housing 72 encircles the piston 80* to prevent leakage of fluid from chamber 89. Any movement of the piston 8% in a brake applying direction spreads the levers 76 at their outer ends thus moving the friction elements 52 axially with respect to the brake axis.

As best seen in FIGURE 3, the levers and link arrangement approximate a parallelogram type linkage permitting relative shifting of the disk friction elements to accommodate them to the drum surfaces. Moreover, the linkage is such that it can follow up to compensate for unequal wear on the two disk friction elements. Also the forces acting on the two friction elements tending to spread them are automatically substantially equalized. The overall linkage combined being such that the levers pivot in a plane parallel to the sides 18 and 20 of the rotatable member as well as perpendicularly thereto.

The disk friction elements 52 are self-energizing upon actuation thereof by fluid motor 70-. Initial engagement of one end of friction elements 52 and the sides of the drum 18 and 29 is produced by the spreading of the outer ends of levers 76. The resulting frictional forces developed between the sides of the drum and the friction elements 52 tend to cause a circumferential movement of friction elements. The ends of the friction elements attached to the outer ends of the levers 76 being constrained to move in an are about the fixed inner ends of the levers (except for axial motion of the piston 80). The frictional forces being opposed by the balls 66' acting on the cam surfaces of members 58 at the opposite ends of friction members 52 causing a spreading of said opposite ends, resulting in further frictional engagement between the friction elements and drum surfaces 18 and 20. The balls 60 transmit the frictional forces from friction elements 52 to the friction element 36, causing it to pivot about its anchor 30 establishing frictional contact with the cylindrical surface of cylindrical portion 16-. The friction element 36 is also self-energizing in the same manner as the shoe of a conventional internal shoe brake.

In order that the shoe element 36 of the friction unit 28 may be adjusted as the lining 64 wears, an adjusting mechanism 86 is provided. The mechanism is supported on the fixed member 14 by a machine bolt 83 threadedly engaging flange 90 of the fluid motor 70, as best shown in FIGURE 5. A gripping member 92 is rotatably carried at the end of the bolt 38. The gripping member is formed with parallel sides 94 and 96, each having an opening 98 and 100 respectively, into which a pin 102 slidably fits. A spring 104 is coiled around the bolt 88 with one end of the spring engaging the fluid motor housing 72 to prevent rotation of the spring and the other end or free end of the spring engaging the gripping member 92, tending to rotate the same clockwise, as viewed in FIGURE 1. The end of the pin 102 opposite the end which slides in the gripping member 92 is bifurcated so as to straddle the web 38. The bifurcations are provided with elongated openings into which a pin 108 extends for limited movement therein. The pin 108 is securely held in the web 38 and projects on each side thereof to thereby engage the elongated openings in the bifurcations. The elongated slots in the bifurcations permit a slight amount of lost motion between the pins 162 and 10 8.

The adjusting mechanism is constructed so that the pin 102, as viewed in FIGURE 1, can be moved upward easily relative to the gripping member 92 but will not move downward because of the high frictional resistance. As a result of each brake application the friction unit 28 is rotated counterclockwise. If there is a substantial amount of wear of the lining 64 as the result of a brake application the pin 1432 will be moved upwardly relative to the member 92 and friction member 28 will on release of the brake be returned an amount equal to the clearance between the hole 106 and the pin 198.

With reference to FIGURE 1 a conduit 110' connects the two cylinders 72 to provide free communication therebetween. A source of fluid under pressure, not shown, is connected to one or the other of the cylinders 72 for actuating the friction units 23.

Operation and performance of the brake of the invention is as follows:

Assume a brake application is made with the rotatable member turning in the direction of the arrow counterclockwise in FIGURE 1. The fluid under pressure acting in the cylinders 72 will move the pistons axially spreading the levers at the outer ends, thus urging the friction elements 52 against the plane surfaces of the sides 18 and 20. The frictional engagement between the friction elements 52 and sides 18 and 20- causes limited rotation of the elements in the direction of rotation of the rotatable member, in this instance, in the direction of the arrow. This rotation of the friction elements 52 relative to the friction element 36 cams the first mentioned friction elements axially against the drum surfaces 18 and 20' augmenting the applying force from the piston and levers. The friction elements 52 anchor through the balls 60 on friction element 36 causing it to frictionally engage the arcuate surface of the cylindrical portion 16 of the rotatable member. As the pressure in the cylinders 72 is increased the frictional forces developed in the friction elements 52 tendingto further rotate the friction element 36 become proportionately greater. When braking in the forward direction, that is, in the direction of the arrow both the'disk and shoe elements are eifective. When the pressure in the cylinders 72 is relieved springs 50 and 59 return the friction unit to released position out of frictional engagement with the rotatable member.

When a brake application is made with drum rotation opposite to that of the arrow, that is, reverse rotation the pistons 80 cause axially spreading of the levers at their outer ends to thereby urge the friction elements 52 against sides 11-8 and 20 in the same manner as previously described for forward rotation. This frictional engagement between the friction elements 52 and the sides creates limited rotation of the element in a clockwise direction. This action of the friction elements 52. relative to the friction element 36 cams the first mentioned friction elements against the sides 18 and 20 thus supplementing the applying [force from the piston and levers. The friction elements 52 anchor through the balls 60 on the friction element 36 pivoting the latter clockwise about anchor 30, as viewed in FIGURE 1. It will be noted that this pivotal action of the element 36 moves the lining 64 of the shoe away from the cylindrical portion :16 of the drum. Hence for reverse braking only the disk elements are effective.

Although this invention has been described in connection with certain specific embodiments, the principles are susceptible of numerous other applications that will read ily occur to persons skilled in the art.

I claim:

1. In a brake, a rotatable element having spaced parallel sides, substantially flat disk friction elements engageable with said sides, a fluid motor having a movable mem ber reciprocably mounted therein, a stationary member, *said fluid motor supported by said stationary member, a pair of levers fulcrumed one against the other and interconnecting said disk friction elements and said movable and stationary members, each of said levers having pivotal connections with said members and to said disk friction elements to pivot about the longitudinal axis of said fluid motor and also pivoting perpendicularly to the parallel sides of said rotatable member.

2. An auxiliary brake applying mechanism comprising: oppositely acting friction members for engagement with opposed brake surfaces, support means, said support means including actuating means, a first lever having one end operatively connected to one of said friction members, a second lever having one end operatively connected to the other of said friction members, the other end of said first lever being swivelably connected to said support means, the other end of said second lever being swivelably connected to said actuating means, said levers being operatively connected to each other by a bearing connection intermediate the ends thereof, each of said levers being actuatable in a plane transverse to the plane of said friction members and so constructed to apply said triction members into engagement with and produce pressure on said brake surfaces, said brake surfaces, said friction member-s and said levers being so constructed and arranged so that said levers will rock as a unit about said 'swivelable connection of each lever to said support means and said actuating means about an axis transverse to said friction members when said friction members are moved by their respective brake surfaces.

3. An auxiliary brake applying mechanism comprising: oppositely acting friction members for engagement with opposed brake surfaces, a first lever having one end operatively connected to one of said friction members, a second lever having one end operatively connected to the other of said friction members, support means for the other end of said second lever, means swivela-bly connecting said other end of said second lever to said support means, said levers being operatively connected to each other by a bearing connection intermediate the end-s thereof, each of said levers being actuable in a plane transverse to the plane of said friction members and so constructed to apply said friction members into engagement with and produce pressure on said brake surfaces, actuating means including a fluid actuating piston, said piston being swivelably connected to the other end of said first lever, said brake surfaces, said friction members and said levers being so constructed and arranged so that said lever-s will pivot as a unit about said swiveiable connections about an axis transverse to said friction members when said friction members are moved by their respective brake surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 1,927,358 Breguet Sept. 19, 1933 2,115,083 Pierce Apr. 26, 1938 2,174,398 Farmer Sept. 26, 1939 2,372,319 Francois Mar. 27, 1945 2,927,663 Burnett Mar. 8, 1960 

1. IN A BRAKE, A ROTATABLE ELEMENT HAVING SPACED PARALLEL SIDES, SUBSTANTIALLY FLAT DISK FRICTION ELEMENTS ENGAGEABLE WITH SAID SIDES, A FLUID MOTOR HAVING A MOVABLE MEMBER RECIPROCABLY MOUNTED THEREIN, A STATIONARY MEMBER, SAID FLUID MOTOR SUPPORTED BY SAID STATIONARY MEMBER, A PAIR OF LEVERS FULCRUMED ONE AGAINST THE OTHER AND INTERCONNECTING SAID DISK FRICTION ELEMENTS AND SAID MOVABLE AND STATIONARY MEMBERS, EACH OF SAID LEVERS HAVING PIVOTAL CONNECTIONS WITH SAID MEMBERS AND TO SAID DISK FRICTION ELEMENTS TO PIVOT ABOUT THE LONGITUDINAL AXIS OF SAID FLUID 